Transmission apparatus, reception apparatus, and transmission and reception system

ABSTRACT

A transmission apparatus transmits a data signal to a reception apparatus with use of a first clock generated on the basis of a clock signal given to the transmission apparatus. The transmission apparatus changes an operation band of a PLL section to an operation band including a frequency of the clock signal which frequency has been measured with use of a second clock independent of the first clock. The transmission apparatus provides the reception apparatus with band information indicative of the operation band to which the operation band of the PLL section has been changed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT International Application No.PCT/JP2014/061406 filed in Japan on Apr. 23, 2014, which claims thebenefit of Patent Application No. 2013-095338 filed in Japan on Apr. 30,2013, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to (i) a transmission apparatus whichtransmits a data signal, (ii) a transmission method of transmitting adata signal, (iii) a reception apparatus which receives a data signal,(iv) a reception method of receiving a data signal, and (v) atransmission and reception system including the transmission apparatusand the reception apparatus.

BACKGROUND ART

A transmission and reception system for transmitting and receiving datasignals often uses a clock signal to determine a transmission clock anda reception clock. In a transmission and reception system, such asCamera Link (Registered Trademark), in which a cycle of a clock signalis not identical to those of a transmission clock and a reception clock,a transmitter and a receiver use respective PLL (Phase Looked Loop)circuits so as to generate a transmission clock from a clock signal orso as to generate a clock signal from a reception clock. For example, inthe Camera Link, a PLL circuit of a transmitter generates a transmissionclock whose cycle is 2/7 times as long as that of a clock signal (whosefrequency is 7/2 times as high as that of the clock signal). Thetransmitter transmits data at every rising edge of and at every fallingedge of the transmission clock. In the Camera Link, a receiverreproduces, from a data signal which the receiver has received, areception clock whose cycle is identical to that of the transmissionclock. A PLL circuit of the receiver restores, from the reception clock,a clock signal whose cycle is 7/2 times as long as that of the receptionclock (whose frequency is 2/7 times as high as that of the receptionclock).

A PLL circuit typically has limitation on its operation band. Therefore,in a case where a bandwidth of a signal which a PLL circuit receives islarge, a plurality of PLL circuits having respective different operationbands are prepared, and one of the plurality of PLL circuits which is tobe used is selected in accordance with a frequency of the signal whichthe PLL circuit receives. The PLL circuit to be used is selected on thebasis of a LOCK signal (which becomes active while the PLL circuit isstably operating) of the PLL circuit. On the other hand, the PLL circuitsometimes maintains a LOCK state in response to an input signal thatexceeds a predetermined operation band. That is, it is difficult tocorrectly determine, from a state of a LOCK signal, whether or not thePLL circuit is properly operating.

In a case where the PLL circuit maintains the LOCK state in response tothe input signal that exceeds the predetermined operation band, it isnecessary to cause the PLL circuit to stably operate by resetting anoperation of the PLL circuit. An example of a method of resetting theoperation of the PLL circuit is a method of resetting the PLL circuit ofthe transmitter which resetting is triggered when the PLL circuit of thereceiver is not in a LOCK state (i.e., an input signal exceeding thepredetermined operation band is inputted). However, there is apossibility that the PLL circuit of the receiver is not optimized likethe PLL circuit of the transmitter. That is, a case can be caused inwhich an operation band of the PLL circuit of the transmitter isinconsistent with that of the PLL circuit of the receiver (the PLLcircuit of the transmitter and the PLL circuit of the receiver operatewithin respective different operation bands). Other examples of themethod of resetting the operation of the PLL circuit are described inPatent Literatures 1 and 2 as below.

Patent Literature 1 describes a PLL circuit which, when a controlelectric potential of a voltage control oscillator circuit (VCO) reachesa predetermined upper limit or lower limit, automatically adjusts thenumber of stages of a ring oscillator to an optimal number of stages sothat an output of the VCO has a desired frequency. The inventiondescribed in Patent Literature 1 makes it possible to reduce gain of theVCO even in a case where a variable frequency band is large. This allowsthe PLL circuit to be resistant to external noise.

Patent Literature 2 describes a clock circuit including (i) a clockcomparator circuit which compares a constant frequency with a clocksignal supplied from an input buffer, (ii) a multiplication settingcircuit which sets a multiplication of a PLL on the basis of amultiplication selection signal, and (iii) a multiplication andfrequency division setting circuit which sets a multiplication value ofthe PLL and a frequency division value of a frequency divider circuit onthe basis of a multiplication and frequency division setting signalsupplied from the multiplication setting circuit. The inventiondescribed in Patent Literature 2 makes it possible to automatically seta multiplication in accordance with a frequency of a bus withoutexternally setting the multiplication.

CITATION LIST Patent Literature

[Patent Literature 1]

Japanese Patent Application Publication, Tokukai, No. 2003-87117(Publication Date: Mar. 20, 2003)

[Patent Literature 2]

Japanese Patent Application Publication, Tokukaihei, No. 10-289032(Publication Date: Oct. 27, 1998)

SUMMARY OF INVENTION Technical Problem

In order to improve stability of communication, it is necessary to causea transmitter and a receiver to share various settings. The transmitterand the receiver should share, for example, setting of operation bandsof PLL circuits.

On the other hand, according to the above conventional techniques, atransmitter and a receiver include respective PLL circuits whoseoperation bands are independently changed. It is therefore uncertainwhether or not the operation band of the PLL circuit of the transmitteris consistent with that of the PLL circuit of the receiver.Inconsistency of the operation bands makes it impossible to correct afrequency even in a case where the PLL circuits are operating withinfrequency bands outside of stable operation ranges. This can cause adefect due to, for example, change of environmental conditions.

The present invention was made in view of the problem, and an object ofthe present invention is to improve stability of communication duringtransmission and reception of data between a transmitter and a receiver.

Solution to Problem

In order to attain the object, a transmission apparatus of the presentinvention is configured to include: a PLL (Phase Looked Loop) sectionwhich generates a first clock on the basis of a clock signal given tothe PLL section; a data signal transmitting section which transmits,with use of the first clock generated by the PLL section, a data signalgiven to the data signal transmitting section together with the clocksignal being given to the PLL section; and a control section whichmeasures a frequency of the clock signal with use of a second clockindependent of the first clock, the control section (i) changing settingof the transmission apparatus to setting corresponding to a measuredfrequency and (ii) providing, with setting information indicative of thesetting to which the setting of the transmission apparatus has beenchanged, a reception apparatus to which the data signal is to betransmitted.

In order to attain the object, a reception apparatus of the presentinvention is configured to include: a data signal receiving sectionwhich (i) reproduces a clock synchronizing with a first clock with useof which a transmission apparatus transmits a data signal, the datasignal receiving section reproducing the clock from the data signalwhich the transmission apparatus has transmitted and (ii) receives, withuse of the clock synchronizing with the first clock, the data signalwhich the transmission apparatus has transmitted; a clock signalrestoring section which restores, on the basis of the clocksynchronizing with the first clock, a clock signal with reference towhich the transmission apparatus generates the first clock; and acontrol section which (i) obtains, from the transmission apparatus,setting information indicative of setting of the transmission apparatusand (ii) changes setting of the reception apparatus to the settingindicated by the setting information.

In order to attain the object, a transmission method of the presentinvention is configured to include the steps of: (a) generating a firstclock on the basis of a clock signal given; (b) transmitting, with useof the first clock generated in the step (a), a data signal giventogether with the clock signal being given; (c) measuring a frequency ofthe clock signal with use of a second clock independent of the firstclock; (d) changing setting of a transmission apparatus to settingcorresponding to a measured frequency; and (e) providing, with settinginformation indicative of the setting to which the setting of thetransmission apparatus has been changed, a reception apparatus to whichthe data signal is to be transmitted.

In order to attain the object, a reception method of the presentinvention is configured to include the steps of: reproducing a clocksynchronizing with a first clock with use of which a transmissionapparatus transmits a data signal, the clock being reproduced from thedata signal which the transmission apparatus has transmitted; receiving,with use of the clock synchronizing with the first clock, the datasignal which the transmission apparatus has transmitted; restoring, onthe basis of the clock synchronizing with the first clock, a clocksignal with reference to which the transmission apparatus generates thefirst clock; obtaining, from the transmission apparatus, settinginformation indicative of setting of the transmission apparatus; andchanging setting of a reception apparatus to the setting indicated bythe setting information.

Advantageous Effects of Invention

According to the present invention, it is possible to improve stabilityof communication during transmission and reception of data between atransmitter and a receiver.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating configurations of a transmissionapparatus and a reception apparatus of Embodiment 1 of the presentinvention.

FIG. 2 is a block diagram illustrating configurations of a transmissionapparatus and a reception apparatus of a modification of Embodiment 1 ofthe present invention.

(a) of FIG. 3 is a block diagram illustrating an example configurationof a PLL section of the transmission apparatus of Embodiment 1 of thepresent invention. (b) of FIG. 3 is a graph illustrating operation bandsof respective PLL circuits included in the PLL section illustrated in(a) of FIG. 3.

(a) of FIG. 4 is a block diagram illustrating a modification of the PLLsection of the transmission apparatus of Embodiment 1 of the presentinvention. (b) of FIG. 4 is a graph illustrating operation bands ofrespective PLL circuits included in a PLL section illustrated in (a) ofFIG. 4.

FIG. 5 is a block diagram illustrating an example configuration of afrequency converting section of the transmission apparatus of Embodiment1 of the present invention.

(a) of FIG. 6 is a block diagram illustrating an example configurationof a control section of the transmission apparatus of Embodiment 1 ofthe present invention. (b) of FIG. 6 is a block diagram illustrating amodification of the control section of the transmission apparatus ofEmbodiment 1 of the present invention.

FIG. 7 is a block diagram illustrating a configuration of a transmissionand reception system in which the transmission apparatus and thereception apparatus of Embodiment 1 of the present invention are appliedto a Camera Link cable.

FIG. 8 is a block diagram illustrating a system configuration whichmakes it possible to share, with another system, a frequency of a clocksignal of the transmission apparatus and the reception apparatus ofEmbodiment 1 of the present invention.

FIG. 9 is a block diagram illustrating configurations of a transmissionapparatus and a reception apparatus of Embodiment 2 of the presentinvention.

FIG. 10 is a block diagram illustrating an example configuration of ajitter removing section included in the transmission apparatus ofEmbodiment 2 of the present invention.

FIG. 11 is a table showing an example correspondence, in thetransmission apparatus of Embodiment 2 of the present invention, among(i) a range of a frequency of a clock signal, (ii) a range of a countvalue outputted from a frequency determining circuit, and (iii)frequency division ratios of respective frequency divider circuitsincluded in the jitter removing section.

(a) of FIG. 12 is a table showing an example correspondence, in thetransmission apparatus of Embodiment 2 of the present invention, among(i) the range of the frequency of the clock signal, (ii) the range ofthe count value outputted from the frequency determining circuit, and(iii) a link command. (b) of FIG. 12 is a table showing an examplecorrespondence, in the reception apparatus of Embodiment 2 of thepresent invention, between (i) a link command and (ii) frequencydivision ratios of respective frequency divider circuits included in ajitter removing section.

FIG. 13 is a block diagram illustrating configurations of a transmissionapparatus and a reception apparatus of Embodiment 3 of the presentinvention.

(a) of FIG. 14 is a table showing an example correspondence, in thetransmission apparatus of Embodiment 3 of the present invention, among(i) a range of a frequency of a clock signal, (ii) a range of a countvalue outputted from a frequency determining circuit, and (iii) a linkcommand. (b) of FIG. 14 is a table showing an example correspondence, inthe reception apparatus of Embodiment 3 of the present invention,between (i) a link command and (ii) frequency division ratios ofrespective frequency divider circuits included in a jitter removingsection.

FIG. 15 is a block diagram illustrating a modification of a jitterremoving section of the transmission apparatus of Embodiment 3 of thepresent invention.

FIG. 16 is a table showing an example correspondence, in thetransmission apparatus of Embodiment 3 of the present invention, among(i) a range of a frequency of a clock signal, (ii) a range of a countvalue outputted from the frequency determining circuit, and (iii)numbers “N” and “M” of each frequency divider circuit included in thejitter removing section.

(a) of FIG. 17 is a table showing an example correspondence, in thetransmission apparatus of Embodiment 3 of the present invention, among(i) a range of a frequency of a clock signal, (ii) a range of a countvalue outputted from the frequency determining circuit, and (iii) a linkcommand. (b) of FIG. 17 is a table showing an example correspondence, inthe reception apparatus of Embodiment 3 of the present invention,between (i) a link command and (ii) numbers “N” and “M” of each of thefrequency divider circuits included in the jitter removing section.

DESCRIPTION OF EMBODIMENTS Embodiment 1

The following description will discuss Embodiment 1 of the presentinvention with reference to the drawings.

[Configurations of Transmission Apparatus and Reception Apparatus]

Configurations of a transmission apparatus 1 and a reception apparatus 2of Embodiment 1 will be described with reference to FIG. 1. FIG. 1 is ablock diagram illustrating configurations of sections of thetransmission apparatus 1 and the reception apparatus 2. The transmissionapparatus 1 is an apparatus configured to transmit a data signal X tothe reception apparatus 2. The reception apparatus 2 is an apparatusconfigured to receive the data signal X from the transmission apparatus1.

Note that the data signal X may be an electrical signal, an opticalsignal, a serial signal, or a parallel signal. For example, in a casewhere the transmission apparatus 1 is used as a camera-side connector inconformity to Camera Link, the data signal X is a parallel signal (datasignals X0 through X3) transmitted through four pairs of electricalsignal lines, or a serial signal into which the parallel signal isserialized, the serial signal being transmitted through a singleelectrical signal line or a pair of electrical signal lines (in a caseof a differential method). Alternatively, in a case where thetransmission apparatus 1 is used as a camera-side connector inconformity to an optical Camera Link, the data signal X is an opticalsignal into which the serial signal is E/O converted, the optical signalbeing transmitted through a signal optical fiber.

As illustrated in FIG. 1, the transmission apparatus 1 includes atransmitter 11 and a control section 12. The transmitter 11 includes adata signal transmitting section 111, a PLL section 112, and a frequencyconverting section 113. The following description will discuss functionsof respective blocks included in the transmission apparatus 1.

The data signal transmitting section 111 is means for transmitting adata signal X to the reception apparatus 2 with use of a clock (firstclock) CLK1 generated in the PLL section 112 (later described), the datasignal X having been supplied from an external apparatus (such as acamera).

The PLL section 112 is means for generating a first clock CLK1 on thebasis of a clock signal Xclk supplied together with a data signal X. InEmbodiment 1, the PLL section 112 generates a clock CLK1 whose frequencyis higher than that of a clock signal Xclk by multiplying the clocksignal Xclk (e.g., by seven or 7/2). The PLL section 112 has a pluralityof switchable operation bands. In Embodiment 1, the PLL section 112 hastwo switchable operation bands overlapping with each other. The clockCLK1 generated by the PLL section 112 is supplied to the data signaltransmitting section 111. Note that a specific example of the PLLsection 112 will be described below with reference to drawings differentfrom FIG. 1.

The frequency converting section 113 is means for converting, into anintermediate clock signal Mclk whose frequency is not more than 1/2 ashigh as that of a clock CLK2 (later described; an operation clock of thecontrol section 12), a clock signal Xclk supplied from an externalapparatus. The intermediate clock signal Mclk obtained in the frequencyconverting section 113 is supplied to the control section 12. Note thata specific example of the frequency converting section 113 will bedescribed below with reference to a drawing different from FIG. 1.

The control section 12 is provided with an OSC (also called anoscillator circuit), and functions to measure a frequency of a clocksignal Xclk with use of a clock (second clock) CLK2 independent of aclock CLK1. In Embodiment 1, the control section 12 measures thefrequency of the clock signal Xclk with reference to an intermediateclock signal Mclk obtained in the frequency converting section 113. Thecontrol section 12 further functions to change an operation band to beused in the PLL section 112 to an operation band of the plurality ofswitchable operation bands which includes the measured frequency of theclock signal Xclk. In Embodiment 1, when the measured frequency of theclock signal Xclk exceeds a predetermined frequency f0 (included in apart where the two operation bands of the PLL section 112 overlap), thecontrol section 12 changes the operation band to be used in the PLLsection 112 to a high-frequency operation band. In contrast, when themeasured frequency of the clock signal Xclk is smaller than thepredetermined frequency f0, the control section 12 changes the operationband to be used in the PLL section 112 to a low-frequency operationband. The control section 12 further functions to provide the receptionapparatus 2 with band information indicative of an operation band towhich the operation band to be used in the PLL 112 has been changed.

The band information with which the control section 12 provides thereception apparatus 2 may directly indicate the operation band to whichthe operation band to be used in the PLL 112 has been changed, or mayindirectly indicate the operation band to which the operation band to beused in the PLL 112 has been changed (e.g., the measured frequency ofthe clock signal Xclk). In other words, the band information is notparticularly limited, provided that the reception apparatus 2 canrecognize which operation band of the PLL section 112 is selected.

The reason why the frequency converting section 113 is provided inEmbodiment 1 is that a case is supposed in which the frequency of theclock signal Xclk (in a case where the frequency of the clock signalXclk varies, an upper limit of a range of the variation) (e.g., 85 MHz)exceeds half of a frequency (e.g., 25 MHz) of the clock CLK2 of thecontrol section 12 (that is, a case where it is difficult to measure thefrequency of the clock signal Xclk with use of the clock CLK2). Like inEmbodiment 1, by generating an intermediate clock signal Mclk which doesnot cause an upper limit of a frequency to exceed half of the frequencyof the clock CLK2 of the control section 12 (for example, by dividingthe frequency of the clock signal xclk by 2^(m) (where m is an integerof 3 or larger)), it is possible for the control section 12 to correctlymeasure the frequency of the clock signal Xclk even in this case.

As illustrated in FIG. 1, the reception apparatus 2 includes a receiver21 and a control section 22. The receiver 21 includes a data signalreceiving section 211, a reception processing section 212, and a PLLsection 213. The following description will discuss functions ofrespective blocks included in the reception apparatus 2.

The data signal receiving section 211 reproduces a clock CLK1 withreference to a data signal X, and receives the data signal X with use ofthe reproduced clock CLK1. In Embodiment 1, the data signal receivingsection 211 reproduces the clock CLK1 with a CDR (Clock Data Recovery)function. The clock CLK1 reproduced by the data signal receiving section211 is supplied to the PLL section 213. The data signal X received bythe data signal receiving section 211 is supplied to the receptionprocessing section 212.

The PLL section 213 is means for restoring a clock signal Xclk on thebasis of a clock CLK1 reproduced by the data signal receiving section211. In Embodiment 1, the PLL section 213 restores a clock signal Xclkwhose frequency is lower than that of a clock CLK1 by dividing afrequency of the clock CLK1 (e.g., multiplying the frequency of theclock CLK1 by 1/7 or 2/7). The PLL section 213 has a plurality ofswitchable operation bands, like the PLL section 112 of the transmissionapparatus 1. In Embodiment 1, the PLL section 213 has two operationbands overlapping with each other. The clock signal Xclk restored by thePLL section 213 is supplied to the reception processing section 212.

The reception processing section 212 carries out reception processing ofa data signal X received by the data signal receiving section 211, withuse of a clock signal Xclk restored by the PLL section 213. An exampleof the reception processing carried out by the reception processingsection 212 is output processing in synchronization with data and aclock. The data signal X whose reception processing has been carried outby the reception processing section 212, and the clock signal Xclkrestored by the PLL section 213 are supplied to an external apparatus(e.g., a grabber).

The control section 22 functions to obtain, from the control section 12of the transmission apparatus 1, band information indicative of anoperation band of the PLL section 112 of the transmission apparatus 1.The control section 22 further functions to change an operation band ofthe PLL section 213 to the operation band indicated by the bandinformation obtained from the control section 12 of the transmissionapparatus 1. In Embodiment 1, when the band information obtained fromthe control section 12 of the transmitting apparatus 1 is directly orindirectly indicative of a high-frequency operation band of theplurality of operation bands of the PLL section 112 of the transmissionapparatus 1, the control section 22 changes the operation band of thePLL section 213 to the high-frequency operation band. In contrast, whenthe band information obtained from the control section 12 of thetransmitting apparatus 1 is directly or indirectly indicative of alow-frequency operation band of the plurality of operation bands of thePLL section 112 of the transmission apparatus 1, the control section 22changes the operation band of the PLL section 213 to the low-frequencyoperation band.

Since the control section 12 of the transmission apparatus 1 uses aclock CLK2 independent of a clock CLK1, the control section 12 cancorrectly measure a frequency of a clock signal Xclk. Furthermore, thetransmission apparatus 1 changes an operation band of the PLL section112 to an operation band including the measured frequency of the clocksignal Xclk, and provides the reception apparatus 2 with bandinformation indicative of the operation band to which the operation bandof the PLL section 112 has been changed. The reception apparatus 2changes an operation band of the PLL section 213 to the operation bandindicated by the band information obtained from the transmissionapparatus 1. According to the above configurations of the transmissionapparatus 1 and the reception apparatus 2, it is possible to equalize(i) the operation band of the PLL section 112 of the transmissionapparatus 1 and (ii) the operation band of the PLL section 213 of thereception apparatus 2 to each other. It is therefore possible to improvestability of communication during transmission and reception of databetween the transmission apparatus and the reception apparatus.

[Modification of Transmission Apparatus 1]

The following description will discuss, with reference to FIG. 2,configurations of modifications of the transmission apparatus 1 and thereception apparatus 2 of Embodiment 1. FIG. 2 is a block diagramillustrating configurations of respective sections of a transmissionapparatus 1 and a reception apparatus 2. Note that, in thismodification, identical reference numerals are given to members havingrespective functions identical to those described in the aboveEmbodiment 1, and their descriptions are omitted. What is speciallydescribed in this modification is that the transmission apparatus 1includes no frequency converting section 113, unlike the configurationillustrated in FIG. 1.

In a case where a frequency of a clock signal Xclk (in a case where thefrequency of the clock signal Xclk varies, an upper limit of a range ofthe variation) (e.g., 85 MHz) does not exceed half of a frequency (e.g.,1 MHz) of a clock CLK2 of a control section 12, the control section 12can correctly measure the frequency of the clock signal Xclk evenwithout any frequency converting section 113 like in this modification.

[Example Configuration of PLL Section 112]

An example configuration of a PLL section 112 will be described belowwith reference to FIG. 3. (a) of FIG. 3 is a block diagram illustratingthe example configuration of the PLL section 112 of the transmissionapparatus 1. (b) of FIG. 3 is a graph illustrating operation bands ofrespective PLL circuits included in the PLL section 112 illustrated in(a) of FIG. 3.

As illustrated in (a) of FIG. 3, the PLL section 112 includes a PLLcircuit 112 a (first PLL circuit), a frequency converting circuit 112 b,a PLL circuit 112 c (second PLL circuit), and a switch 112 d. Functionsof respective blocks included in the PLL section 112 will be describedbelow. Note that the PLL section 112 is realized with, for example, aFPGA (Field Programmable Gate Array). Note, however, that the presentinvention is not limited to this.

The PLL circuit 112 a is means for generating a clock (first originalclock) CLK3′. In Embodiment 1, the PLL circuit 112 a multiplies afrequency of a clock signal Xclk by 14 to generate a clock CLK3′ whosefrequency is higher than that of the clock signal Xclk. In Embodiment 1,the PLL circuit 112 a has an operation band (first operation band) ofnot lower than 20 MHz and not higher than 70 MHz (see (b) of FIG. 3).The clock CLK3′ generated by the PLL circuit 112 a is supplied to thefrequency converting circuit 112 b.

The PLL circuit 112 c is means for generating a clock (second originalclock) CLK4. In Embodiment 1, the PLL circuit 112 c multiplies afrequency of a clock signal Xclk by 7 to generate a clock CLK4 whosefrequency is higher than that of the clock signal Xclk. In Embodiment 1,the PLL circuit 112 c has an operation band (second operation band)partially overlapping with the operation band of the PLL circuit 112 aand being not lower than 50 MHz and not higher than 85 MHz (see (b) ofFIG. 3). The clock CLK4 generated by the PLL circuit 112 c is suppliedto a terminal of the switch 112 d.

The frequency converting circuit 112 b is provided between the PLLcircuit 112 a and the switch 112 d, and is means for equalizing (i) thefrequency of the clock CLK4 to be supplied to the switch 112 d and (ii)a frequency of a clock CLK3 to be supplied to the switch 112 d to eachother. In Embodiment 1, the frequency converting circuit 112 bmultiplies, by 7/14, i.e., 1/2, the clock CLK3′ generated by the PLLcircuit 112 a so that the frequency converting circuit 112 b generatesthe clock CLK3 whose frequency equals to that of the clock CLK4generated by the PLL circuit 112 c. The clock CLK3 generated by thefrequency converting circuit 112 b is supplied to another terminal ofthe switch 112 d.

The switch 112 d is means for switching between connecting the PLLcircuit 112 a to a data signal transmitting section 111 and connectingthe PLL circuit 112 c to the data signal transmitting section 111. InEmbodiment 1, the switch 112 d is controlled by the control section 12.How the control section 12 controls the switch 112 d will be describedwith reference to (b) of FIG. 3.

In Embodiment 1, the control section 12 functions to change an operationband of the PLL section 112 to an operation band including a measuredfrequency of a clock signal Xclk. As illustrated in (b) of FIG. 3, theoperation band of the PLL circuit 112 a and the operation band of thePLL circuit 112 c partially overlap with each other. When the measuredfrequency of the clock signal Xclk exceeds a predetermined frequency f0(included in a part where two operation bands of the PLL section 112overlap), the control section 12 changes the operation band of the PLLsection 112 to a high-frequency operation band. In contract, when themeasured frequency of the clock signal Xclk is smaller than thepredetermined frequency f0, the control section 12 changes the operationband of the PLL section 112 to a low-frequency operation band. InEmbodiment 1, the predetermined frequency f0 is 60 MHz. Note, however,that the present invention is not limited to this, provided that a valueincluded in a part where the operation band of the PLL circuit 112 a andthe operation band of the PLL circuit 112 c overlap is used as athreshold. For example, in Embodiment 1, any value between a lower limitof the operation band of the PLL circuit 112 c and an upper limit of theoperation band of the PLL circuit 112 a, i.e., any value of not lowerthan 50 MHz and not higher than 70 MHz may be used as the predeterminedfrequency f0. Note that, like in Embodiment 1, it is preferable to use,as the threshold, a substantial median between the lower limit of theoperation band of the PLL circuit 112 c and the upper limit of theoperation band of the PLL circuit 112 a. Use of the substantial medianas the threshold allows adaptation, with a margin, to environmentalconditions such as temperature and noise. This brings about an effectthat a problem such as malfunction is unlikely to occur.

In Embodiment 1, when a frequency of a clock signal Xclk which frequencyhas been measured by the control section 12 is not lower than 60 MHz,the control section 12 controls the switch 112 d to switch so that aclock CLK4 generated by the PLL circuit 112 c is supplied as a clockCLK1 to the data signal transmitting section 111. In contrast, when thefrequency of the clock signal Xclk which frequency has been measured bythe control section 12 is lower than 60 MHz, the control section 12controls the switch 112 d to switch so that a clock CLK3 generated bythe frequency converting circuit 112 b is supplied as a clock CLK1 tothe data signal transmitting section 111.

As such, the control section 12 can suitably change the operation bandof the PLL section 112.

[Modification of PLL Section 112]

A modification of the PLL section 112 will be described below withreference to FIG. 4. (a) of FIG. 4 is a block diagram illustrating themodification of the PLL section 112 of the transmission apparatus 1. (b)of FIG. 4 is a graph illustrating operation bands of respective PLLcircuits included in a PLL section 112 illustrated in (a) of FIG. 4.What is specially described in this modification is that the PLL section112 includes a plurality of frequency converting circuits.

As illustrated in (a) of FIG. 4, the PLL section 112 includes a PLLcircuit 112 a, a frequency converting circuit 112 b, a PLL circuit 112c, a switch 112 d, and a frequency converting circuit 112 e. In thismodification, identical reference numerals are given to members havingrespective functions identical to those described in the aboveEmbodiment 1, and their descriptions are omitted. Note that the PLLsection 112 of this modification is also realized with, for example, aFPGA (Field Programmable Gate Array). Note, however, that the presentinvention is not limited to this.

The PLL circuit 112 a is means for generating a clock CLK3′. In thismodification, the PLL circuit 112 a multiplies a frequency of a clocksignal Xclk by 28 to generate a clock CLK3′ whose frequency is higherthan that of the clock signal Xclk. In this modification, the PLLcircuit 112 a has an operation band of not lower than 20 MHz and nothigher than 70 MHz (see (b) of FIG. 4). The clock CLK3′ generated by thePLL circuit 112 a is supplied to the frequency converting circuit 112 b.

The PLL circuit 112 c is means for generating a clock CLK4′. In thismodification, the PLL circuit 112 c multiplies a frequency of a clocksignal Xclk by 14 to generate a clock CLK4′ whose frequency is higherthan that of the clock signal Xclk. In this modification, the PLLcircuit 112 c has an operation band partially overlapping with theoperation band of the PLL circuit 112 a and being not lower than 50 MHzand not higher than 85 MHz (see (b) of FIG. 4). The clock CLK4′generated by the PLL circuit 112 c is supplied to the frequencyconverting circuit 112 e.

The frequency converting circuit 112 b and the frequency convertingcircuit 112 e are provided between the PLL circuit 112 a and the switch112 d and/or between the PLL circuit 112 c and the switch 112 d. Thefrequency converting circuit 112 b and the frequency converting circuit112 e are means for equalize (i) a frequency of a clock CLK3 to besupplied to the switch 112 d and (ii) a frequency of a clock CLK4 to besupplied to the switch 112 d to each other.

In this modification, the frequency converting circuit 112 b is providedbetween the PLL circuit 112 a and the switch 112 d, and multiplies, by1/4, a clock CLK3′ generated by the PLL circuit 112 a so that thefrequency converting circuit 112 b generates a clock CLK3. The clockCLK3 generated by the frequency converting circuit 112 b is supplied toa terminal of the switch 112 d.

In this modification, the frequency converting circuit 112 e is providedbetween the PLL circuit 112 c and the switch 112 d, and multiplies, by1/2, a clock CLK4′ generated by the PLL circuit 112 c so that thefrequency converting circuit 112 e generates a clock CLK4. The clockCLK4 generated by the frequency converting circuit 112 e is supplied toanother terminal of the switch 112 d.

In this modification, the above-described processing equalizes (i) thefrequency of the clock CLK3 generated by the frequency convertingcircuit 112 b and (ii) the frequency of the clock CLK4 generated by thefrequency converting circuit 112 e to each other.

The switch 112 d is means for switching between connecting the PLLcircuit 112 a to the data signal transmitting section 111 and connectingthe PLL circuit 112 c to the data signal transmitting section 111. Alsoin this modification, the switch 112 d is controlled by the controlsection 12. How the control section 12 controls the switch 112 d issimilar to an example illustrated in FIG. 3, and therefore, descriptionthereof is omitted.

What have been described with reference to FIGS. 3 and 4 are exampleconfigurations of the PLL sections 112 each including (1) the first PLLcircuit 112 a, (2) the second PLL circuit 112 c, and (3) the switch 112d which switches between connecting the first PLL circuit 112 a to thedata signal transmitting section 111 and connecting the second PLLcircuit 112 c to the data signal transmitting section 111. However, theconfigurations of the PLL sections 112 are not limited to these exampleconfigurations. That is, for example, a FPGA (Field Programmable GateArray) which switches, through reconfiguration processing, betweenoperating as the first PLL circuit and operating as the second PLLcircuit may be used as the PLL sections 112.

An example configuration of the frequency converting section 113 will bedescribed below with reference to FIG. 5. FIG. 5 is a block diagramillustrating the example configuration of the frequency convertingsection 113 of the transmission apparatus 1.

As illustrated in FIG. 5, the frequency converting section 113 includesa 2¹⁶ frequency divider circuit 113 a. A function of a block included inthe frequency converting section 113 will be described as follows. Notethat the frequency converting section 113 is realized with a FPGA (FieldProgrammable Gate Array). Note, however, that the present invention isnot limited to this.

The 2¹⁶ frequency divider circuit 113 a is means for generating anintermediate clock signal Mclk by multiplying a frequency of a clocksignal Xclk by 1/2¹⁶, i.e., 1/65536. The intermediate clock signal Mclkgenerated by the 2¹⁶ frequency divider circuit 113 a is supplied to thecontrol section 12. The intermediate clock signal Mclk has a waveformobtained by elongating a waveform of the clock signal Xclk in atime-axis direction.

In the example illustrated in FIG. 5, the control section 12 functionsto measure the frequency of the clock signal Xclk with reference to theintermediate clock signal Mclk. The control section 12 measures thefrequency of the clock signal Xclk with use of a clock CLK2 independentof a clock CLK1. In Embodiment 1, in a case where a pulse width of theintermediate signal Mclk is 1.09 ms, and a predetermined number is 2¹⁶(65536), the control section 12 measures the frequency of the clocksignal Xclk with use of the clock CLK2 independent of the clock CLK1 at(65536/1.09 ms)=60 MHz. Note that processing after the control section12 measures the frequency of the clock signal Xclk is similar to thatdescribed above, and therefore, description of the processing isomitted.

[Example Configuration of Control Section 12]

An example configuration of the control section 12 will be describedbelow with reference to FIG. 6. (a) of FIG. 6 is a block diagramillustrating the example configuration of the control section 12 of thetransmission apparatus of Embodiment 1. (b) of FIG. 6 is a block diagramillustrating a modification of the control section 12 of thetransmission apparatus of Embodiment 1 of the present invention.

In the example illustrated in (a) of FIG. 6 (hereinafter also called“example configuration (a)”), the control section 12 includes an MCU 121and an OSC 122. Functions of respective blocks included in the controlsection 12 will be described as follows.

The OSC 122 is an oscillator circuit configured to generate a clock CLK2independent of a clock CLK1. The MCU 121 functions to measure afrequency of a clock signal Xclk with use of the clock CLK2 generated bythe OSC 122. In the example configuration (a), the MCU 121 is providedwith an input pin (not illustrated) and an INT pin (interrupt pin) (notillustrated).

In the example configuration (a), when a frequency of the clock CLK2 islower than that of the clock signal Xclk, the MCU 121 measures thefrequency of the clock signal Xclk with reference to an intermediateclock signal Mclk obtained in the frequency converting section 113. Incontrast, when the frequency of the clock CLK2 is higher than that ofthe clock signal Xclk, the MCU 121 measures the frequency of the clocksignal Xclk with reference to the clock signal Xclk itself.

In the example configuration (a), when the intermediate clock signalMclk obtained in the frequency converting section 113 or the clocksignal Xclk is supplied to the input pin of the MCU 121, the MCU 121measures the frequency of the clock signal Xclk with reference to aninput level of the supplied intermediate clock signal Mclk or clocksignal Xclk.

In the example configuration (a), when the intermediate clock signalMclk obtained in the frequency converting section 113 or the clocksignal Xclk is supplied to the INT pin of the MCU 121, the MCU 121measures the frequency of the clock signal Xclk by referring to a risingtiming of and a falling timing of the supplied intermediate clock signalMclk or clock signal Xclk through interrupt processing.

The MCU 121 functions to change an operation band of a PLL section 112to an operation band including the measured frequency of the clocksignal Xclk. In the example configuration (a), when the measuredfrequency of the clock signal Xclk exceeds a predetermined frequency f0(included in a part where two operation bands of the PLL section 112overlap), the MCU 121 changes the operation band of the PLL section 112to a high-frequency operation band. In contract, when the measuredfrequency of the clock signal Xclk is smaller than the predeterminedfrequency f0, the MCU 121 changes the operation band of the PLL section112 to a low-frequency operation band. The MCU 121 further functions toprovide the control section 22 of the reception apparatus 2 with bandinformation indicative of an operation band to which the operation bandof the PLL section 112 has been changed.

In an example illustrated in (b) of FIG. 6 (hereinafter also called“example configuration (b)”), a control section 12 includes an MCU 121,an OSC 122, a register circuit 123, and an OSC 124. Functions ofrespective blocks included in the control section 12 will be describedas follows.

The OSC 124 is an oscillator circuit configured to generate a clock CLK2(second clock) independent of a clock CLK1. The register circuit 123functions to measure a frequency of a clock signal Xclk with use of theclock CLK2 generated by the OSC 124.

In the example configuration (b), when a frequency of the clock CLK2 islower than that of the clock signal Xclk, the register circuit 123measures the frequency of the clock signal Xclk with use of the clockCLK2 by referring, to an intermediate clock signal Mclk obtained in thefrequency converting section 113. In contrast, when the frequency of theclock CLK2 is higher than that of the clock signal Xclk, the registercircuit 123 measures the frequency of the clock signal Xclk with use ofthe clock CLK2.

The register circuit 123 functions to change an operation band of thePLL section 112 to an operation band including the measured frequency ofthe clock signal Xclk. In the example configuration (b), when themeasured frequency of the clock signal Xclk exceeds a predeterminedfrequency f0 (included in a part where two operation bands of the PLLsection 112 overlap), the register circuit 123 changes the operationband of the PLL section 112 to a high-frequency operation band. Incontract, when the measured frequency of the clock signal Xclk issmaller than the predetermined frequency f0, the register circuit 123changes the operation band of the PLL section 112 to a low-frequencyoperation band.

Moreover, the register circuit 123 generates frequency data indicativeof the measured frequency of the clock signal Xclk. The frequency datagenerated by the register circuit 123 is supplied to the MCU 121connected to the register circuit 123 via an I2C data bus. Note that thefrequency data generated by the register circuit 123 is preferably avalue indicative of the frequency of the clock signal Xclk. Note,however, that the frequency data generated by the register circuit 123is not limited to the value. That is, the frequency data generated bythe register circuit 123 is not particularly limited, provided that thefrequency data generated by the register circuit 123 is data from whichthe MCU 121 can identify the frequency of the clock signal Xclk, andtherefore may be (i) signal data whose frequency equals to that of theclock signal Xclk or (ii) data indicative of a pulse width of the clocksignal Xclk.

In the example configuration (b), the OSC 122 is an oscillator circuitconfigured to generate a clock CLK5 independent of (i) a clock CLK1 and(ii) a clock CLK2. In the example configuration (b), the MCU 121functions to transmit, with use of the clock CLK5, to the controlsection 22 of the reception apparatus 2, frequency data supplied fromthe register circuit 123.

[Example of Application to Camera Link System]

The transmission apparatus 1 and the reception apparatus 2 of Embodiment1 are applicable to a Camera Link system. The following description willdiscuss, with reference to FIG. 7, an example in which the transmissionapparatus 1 and the reception apparatus 2 of Embodiment 1 are applied tothe Camera Link system. FIG. 7 is a block diagram of a Camera Linksystem including the transmission apparatus 1 and the receptionapparatus 2 of Embodiment 1 as a camera-side connector and agrabber-side connector.

As illustrated in FIG. 7, the transmission apparatus 1 and the receptionapparatus 2 are connected to each other via a cable 3. The transmissionapparatus 1 and the reception apparatus 2 are hereinafter referred to asa camera-side connector 1 and a grabber-side connector 2, respectively.The cable 3 connects a camera to a grabber in conformity to Camera Link.

The camera-side connector 1 includes a transmitter 11. The transmitter11 is a transmission device configured to transmit data signals X0through X3 and a clock signal Xclk which are electrical signals suppliedfrom the camera.

The transmitter 11 is connected to a cable 32 housed by the cable 3. Thetransmitter 11 transmits the data signals X0 through X3 to a grabberside via the cable 32. A grabber side of the cable 32 is connected to areceiver 21 included in the grabber-side connector 2. The receiver 21supplies the received data signals X0 through X3 and a restored clocksignal Xclk to the grabber. A control section 12 connected to thetransmitter 11 and a control section 22 connected to the receiver 21transmit and receive an internal link signal therebetween via a cable31. Note here that the internal link signal is a signal other than acontrol signal (e.g., later-described control signals CC0 through CC3)defined by standards (Camera Link), the signal being indicative ofinternal control information, i.e., a control signal whose externalreference is not defined by standards. Examples of the controlinformation transmittable and receivable as the internal link signalinclude (i) temperature, (ii) internal voltage, (iii) setting values ormonitoring values of bias electric current, modulation electric current,light-emitting power, light-receiving power, etc. of an E/O convertingsection and an O/E converting section (which will be later described),(iv) a LOCK signal from a deserializer, and the like. In Embodiment 1,the camera-side connector 1 supplies band information together withanother control information as the internal link signal to thegrabber-side connector 2, the band information being indicative of anoperation band of a PLL section 112 included in the transmitter 11. Uponreception of control signal including the band information indicative ofthe operation band of the PLL section 12, the grabber-side connector 2changes, to an operation band including a frequency indicated by theband information, an operation band of a PLL section 213 included in thereceiver 21.

The cable 3 further houses (i) a cable 33 via which a down serial signalis transmitted, (ii) a cable 34 via which control signals CC0 throughCC3 are transmitted, and (iii) a cable 35 via which an up serial signalis transmitted. The cables 31 through 35 housed by the cable 3 are allelectrical signal lines. However, the present invention is not limitedto this. For example, any or all of the cables 31 through 35 may bereplaced with an optical fiber(s). The cable 32 that is a high-speedsignal line may be replaced with an optical fiber. In the above case,the camera-side connector 1 further includes an E/O converting sectionwhich converts an electrical signal into an optical signal, and thegrabber-side connector 2 further includes an O/E converting sectionwhich converts an optical signal into an electrical signal.

In a transmission and reception system configured as above, the controlsection 12 of the camera-side connector 1 is connected to the controlsection 22 of the grabber-side connector 22 via the cable 31. InEmbodiment 1, the control section 12 and the control section 22 transmitand receive band information therebetween as an internal link signal.Therefore, the transmission and reception system can improve stabilityof communication during transmission and reception of data between thetransmission apparatus and the reception apparatus.

[Share with Another System]

The following description will discuss, with reference to FIG. 8, a casewhere a frequency of a clock signal Xclk which frequency thetransmission apparatus 1 has measured is shared with another apparatus.FIG. 8 is a block diagram illustrating a system configuration whichmakes it possible to share, with another system, a frequency of a clocksignal Xclk given to the transmission apparatus 1 of Embodiment 1.

As illustrated in FIG. 8, the transmission apparatus 1 is connected tothe reception apparatus 2 via a cable 3. As has been described, thecontrol section 12 included in the transmission apparatus 1 shares bandinformation with the control section 22 included in the receptionapparatus 2 via the cable 3. This makes it possible to equalize (i) theoperation band of the PLL section 112 and (ii) the operation band of thePLL section 213 to each other. Note that a Base cable is used as thecable 3. The transmission apparatus 1, the reception apparatus 2, andthe cable 3 constitute a “Base Configuration” in conformity to CameraLink.

In Embodiment 1, the band information transmitted and received betweenthe transmission apparatus 1 and the reception apparatus 2 can be sharedfurther with another apparatus. In Embodiment 1, the control section 22included in the reception apparatus 2 is connected via a synchronizationcable to a control section 52 included in a reception apparatus 5 (seeFIG. 8). The control section 52 included in the reception apparatus 5 isfurther connected via a cable 6 to a control section 42 included in atransmission apparatus 4. Note that, in a case where the cable 6 is aBase cable, a system illustrated in FIG. 8 has the “MediumConfiguration” in conformity to Camera Link. In a case where the cable 6is a Full cable, the system illustrated in FIG. 8 has a “FullConfiguration” in conformity to Camera Link. The transmission apparatus4 and the reception apparatus 5 function in the same manner as thetransmission apparatus 1 and the reception apparatus 2, respectively.Therefore, descriptions of the transmission apparatus 4 and thereception apparatus 5 are omitted.

Since the reception apparatus 2 is connected to the reception apparatus5 via the synchronization cable, it is possible to share bandinformation between transmission and reception systems different fromeach other. Therefore, a more highly stable communication is attained.Note that Embodiment 1 has described a case where two transmission andreception systems share band information. Note, however, that thepresent invention is not limited to the case. A configuration may beemployed in which three or more transmission and reception systems shareband information.

Embodiment 2

The following description will discuss Embodiment 2 of the presentinvention with reference to drawings.

[Configurations of Transmission Apparatus and Reception Apparatus]

Configurations of a transmission apparatus 1′ of and a receptionapparatus 2′ of Embodiment 2 of the present invention will be describedwith reference to FIG. 9. FIG. 9 is a block diagram illustrating theconfigurations of the transmission apparatus 1′ and the receptionapparatus 2′ of Embodiment 2.

The transmission apparatus 1′ is an apparatus configured to transmit adata signal X to the reception apparatus 2′. The transmission apparatus1′ includes a transmitter 11, a control section 12, and a jitterremoving section 13. The transmitter 11 and the control section 12 whichare included by the transmission apparatus 1′ of Embodiment 2 are blockswhose respective functions identical to those of the transmitter 11 andthe control section 12 which are included by the transmission apparatus1 (particularly, the transmission apparatus 1 illustrated in FIG. 2) ofEmbodiment 1. Therefore, descriptions of the transmitter 11 and thecontrol section 12 which are included by the transmission apparatus 1′of Embodiment 2 are omitted here.

The jitter removing section 13 is configured to remove jitter includedin a clock signal Xclk. In Embodiment 2, a clock signal which thetransmitter 11 receives is a clock signal X′clk from which the jitterremoving section 13 has removed jitter. Similar to the PLL section 112of Embodiment 1, the jitter removing section 13 is configured so that anoperation band is changeable. Note that an example configuration of thejitter removing section 13 whose operation band is changeable will bedescribed later with reference to another drawing.

The control section 12 changes the operation band of the jitter removingsection 13. That is, the control section 12 changes the operation bandof the jitter removing section 13 to an operation band corresponding toa frequency of a clock signal Xclk which frequency has been determinedby a frequency determining circuit 125. The control section 12 alsoprovides the reception apparatus 2′ with a link command corresponding tothe frequency of the clock signal Xclk which frequency has beendetermined by the frequency determining circuit 125. The link commandand the operation band of the jitter removing section 13 have acorrespondence relation via the frequency of the clock signal Xclk.Therefore, the link command can be regarded as band informationindicative of the operation band of the jitter removing section 13. Notethat change of the operation band of the jitter removing section 13, anda specific example of the link command will be described later withreference to another drawing.

Note that the control section 12 is provided with an OSC. The frequencydetermining circuit 125 determines (measures) the frequency of the clocksignal Xclk with use of a clock oscillated by the OSC.

The reception apparatus 2′ is an apparatus configured to receive a datasignal X from the transmission apparatus 1′. The reception apparatus 2′includes a receiver 21, a control section 22, and a jitter removingsection 23. The receiver 21 and the control section 22 which areincluded by the reception apparatus 2′ of Embodiment 2 are blocks whoserespective functions identical to those of the receiver 21 and thecontrol section 22 which are included by the reception apparatus 2(particularly, the reception apparatus 2 illustrated in FIG. 2) ofEmbodiment 1. Therefore, descriptions of the receiver 21 and the controlsection 22 which are included by the reception apparatus 2′ ofEmbodiment 2 are omitted here. Note, however, that a PLL section 213(not illustrated in FIG. 9) included in the receiver 21 may be replacedwith a retiming circuit, a frequency divider circuit or the like whosefunction is identical to that of a PLL circuit.

Similar to the jitter removing section 13 included by the transmissionapparatus 1′, the jitter removing section 23 is configured to removejitter included in a clock signal Xclk. In Embodiment 2, the jitterremoving section 23 removes jitter from a clock signal Xclk having beensupplied from the receiver 21, and outputs outside the clock signal Xclkfrom which the jitter has been removed. Similar to the jitter removingsection 13 included by the transmission apparatus 1′, the jitterremoving section 23 is configured so that an operation band ischangeable.

The control section 22 changes the operation band of the jitter removingsection 23. That is, the control section 22 changes the operation bandof the jitter removing section 23 to an operation band corresponding toband information obtained from the transmission apparatus 1′. Thisuniformalizes (i) setting of the operation band of the jitter removingsection 13 included by the transmission apparatus 1′ to (ii) setting ofthe operation band of the jitter removing section 23 included by thereception apparatus 2′.

Similar to the transmitter 11 of the transmission apparatus 1 ofEmbodiment 1, the transmitter 11 of the transmission apparatus 1′ ofEmbodiment 2 includes a PLL section 112 (see FIG. 2). Similar to thecontrol section 12 of the transmission apparatus 1 of Embodiment 1, thecontrol section 12 of the transmission apparatus 1′ of Embodiment 2changes an operation band of the PLL section 112 to an operation bandincluding a frequency of a clock signal Xclk, and provides the receptionapparatus 2′ with band information indicative of the operation band towhich the operation band of the PLL section 112 has been changed.Similar to the receiver 21 of the reception apparatus 2 of Embodiment 1,the receiver 21 of the reception apparatus 2′ of Embodiment 2 includesthe PLL section 213 (see FIG. 2). Similar to the control section 22 ofthe reception apparatus 2 of Embodiment 1, the control section 22 of thereception apparatus 2′ of Embodiment 2 obtains the band information fromthe transmission apparatus 1′, and changes an operation band of the PLLsection 213 to the operation band indicated by the obtained bandinformation. This links (i) setting of the operation band of the PLLsection 112 included by the transmission apparatus 1′ to (ii) setting ofthe operation band of the PLL section 213 included by the receptionapparatus 2′.

As such, in Embodiment 2, (i) the setting of the operation band of thejitter removing section 13 included by the transmission apparatus 1′ andthe setting of the operation band of the jitter removing section 23included by the reception apparatus 2′ are linked to each other, and(ii) the setting of the operation band of the PLL section 112 includedby the transmission apparatus 1′ and the setting of the operation bandof the PLL section 213 included by the reception apparatus 2′ are linkedto each other. Alternatively, it may be such that (i) the setting of theoperation band of the PLL section 112 and the setting of the operationband of the PLL section 213 are not linked to each other, and (ii) onlythe setting of the operation band of the jitter removing section 13 andthe setting of the operation band of the jitter removing section 23 arelinked to each other.

Similar to the transmission apparatus 1 and the reception apparatus 2 ofEmbodiment 1, the transmission apparatus 1′ and the reception apparatus2′ of Embodiment 2 are applicable to a Camera Link system (see FIG. 7).That is, the transmission apparatus 1′ and the reception apparatus 2′ ofEmbodiment 2 are applicable to a camera-side connector and agrabber-side connector of the Camera Link system. In this case, theabove-described link command (the band information indicative of theoperation band of the jitter removing section 13), for example, istransmittable as an internal link signal, together with another controlinformation, from the transmission apparatus 1′ that is the camera-sideconnector to the reception apparatus 2′ that is the grabber-sideconnector.

[Example Configuration of Jitter Removing Section 13]

The example configuration of the jitter removing section 13 included bythe transmission apparatus 1′ will be described with reference to FIG.10. FIG. 10 is a block diagram illustrating the example configuration ofthe jitter removing section 13.

The jitter removing section 13 is a jitter cleaner whose operation bandis changeable (whose frequency division ratio is changeable). Asillustrated in FIG. 10, the jitter removing section 13 includes a firstfrequency divider circuit 131, a second frequency divider circuit 132, aphase comparator 133, a loop filter 134, a VCO (voltage controloscillator circuit) 135, a third frequency divider circuit 136, and afourth frequency divider circuit 137. Functions of respective blocksincluded in the jitter removing section 13 will be described as follows.

The first frequency divider circuit 131 is a frequency divider circuitwhose frequency division ratio is changeable and which uses, as thefrequency division ratio, a value A written in a register (notillustrated). The first frequency divider circuit 131 receives a clocksignal Xclk, and outputs a clock signal whose frequency is 1/A as highas that of the clock signal Xclk. The second frequency divider circuit132 is a frequency divider circuit whose frequency division ratio ischangeable and which uses, as the frequency division ratio, a value Bwritten in a register (not illustrated). The second frequency dividercircuit 132 receives a clock signal supplied from the third frequencydivider circuit 136, and outputs a clock signal whose frequency is 1/Bas high as that of the received clock signal. The clock signalsoutputted from the first frequency divider circuit 131 and the secondfrequency divider circuit 132 are supplied to the phase comparator 133.

The phase comparator 133 generates a phase difference signal having avalue proportional to a phase difference between the clock signaloutputted from the first frequency divider circuit 131 and the clocksignal outputted from the second frequency divider circuit 132(specifically, the phase comparator 133 generates a voltage signal whosevoltage is proportional to the phase difference). The phase differencesignal generated by the phase comparator 133 is smoothed by the loopfilter 134, and then supplied to the VCO 135.

The VCO 135 generates a clock signal having a frequency proportional toa value of the smoothed phase difference signal. The clock signalgenerated by the VCO 135 is supplied to the third frequency dividercircuit 136.

The third frequency divider circuit 136 is a frequency divider circuitwhose frequency division ratio is changeable and which uses, as thefrequency division ratio, a value C written in a register (notillustrated). The third frequency divider circuit 136 receives the clocksignal generated by the VCO 135, and outputs a clock signal whosefrequency is 1/C as high as that of the clock signal generated by theVCO 135. The clock signal outputted from the third frequency dividercircuit 136 is supplied to the second frequency divider circuit 132 andthe fourth frequency divider circuit 137. Note that a frequency divisionratio C of the third frequency divider circuit 136 may be fixed.

The fourth frequency divider circuit 137 is a frequency divider circuitwhose frequency division ratio is changeable and which uses, as thefrequency division ratio, a value D written in a register (notillustrated). The fourth frequency divider circuit 137 receives theclock signal outputted from the third frequency divider circuit 136, andoutputs a clock signal whose frequency is 1/D as high as that of theclock signal outputted from the third frequency divider circuit 136.Output from the fourth frequency divider circuit 137 is output from thejitter removing section 13. That is, the clock signal outputted from thefourth frequency divider circuit 137 is a clock signal X′clk.

As such, the jitter removing section 13 includes negative feedbackcircuits which equalize, to zero, the phase difference (frequencydifference) between the clock signal outputted from the first frequencydivider circuit 131 and the clock signal outputted from the secondfrequency divider circuit 132. Therefore, assuming that (i) a frequencyof the clock signal Xclk which the first frequency divider circuit 131receives is fclk and (ii) a frequency of the clock signal outputted fromthe VCO 135 is fvco, the jitter removing section 13 operates so thatfclk/A=fvco/(B×C). Accordingly, provided that frequency division ratiosA, B and D are set so that B=A×D is satisfied, a frequency f′clk(=fvco/(C×D)) of the clock signal X′clk outputted from the jitterremoving section 13 equals to the frequency fclk of the clock signalXclk which the jitter removing section 13 receives.

As a time constant of the loop filter 134 increases, response speed ofthe jitter removing section 13 decreases. That is, the frequency f′clkof the clock signal X′clk outputted from the jitter removing section 13has difficulty conforming to the frequency fclk of the clock signal Xclkwhich the jitter removing section 13 receives. This makes it possible tosuppress fluctuation of the frequency of the clock signal Xclk which thejitter removing section 13 receives, that is, to remove jitter includedin the clock signal Xclk which the jitter removing section 13 receives.

Changing the operation band of the jitter removing section 13 isrealized by rewriting of the frequency division ratios A through Dwritten in the registers. In a case where the frequency of the clocksignal Xclk is too high or too low, a case will occur in which thefrequencies of the clock signals which the phase comparator 133 receivesexceed an upper limit of the operation band of the jitter removingsection 13 or is lower than a lower limit of the operation band of thejitter removing section 13. However, it is possible to prevent the casefrom occurring by changing the operation band of the jitter removingsection 13 to an operation band corresponding to the clock signal Xclk,that is, by setting the frequency division ratios A through D to valuescorresponding to the frequency of the clock signal Xclk.

Note that the jitter removing section 23 of the reception apparatus 2′is configured in the same manner as the jitter removing section of thetransmission apparatus 1′.

[Changing Operation Band of Jitter Removing Section 13]

As has been described, the control section 12 of the transmissionapparatus 1′ changes the operation band of the jitter removing section13 to the operation band corresponding to the frequency of the clocksignal Xclk which frequency has been determined by the frequencydetermining circuit 125. In a case where the jitter cleaner illustratedin FIG. 10 is used as the jitter removing section 13, the frequencydivision ratios A through D of the respective frequency divider circuits131, 132, 136 and 137 included in the jitter removing section 13 arechanged to values corresponding to a range of a count value outputtedfrom the frequency determining circuit 125.

FIG. 11 shows an example correspondence among (i) a range of thefrequency fclk of the clock signal Xclk, (ii) the range of the countvalue outputted from the frequency determining circuit 125, and (iii)the frequency division ratios A through D of the respective frequencydivider circuits 131, 132, 136 and 137 included in the jitter removingsection 13.

For example, in a case where the range of the frequency fclk of theclock signal Xclk is not lower than 19 MHz and not higher than 21 MHz,the range of the count value outputted from the frequency determiningcircuit 125 is not less than 435E and not more than 3B91. In this case,the control section 12 sets, to 100, 5000, 2 and 50, the frequencydivision ratios A through D of the respective frequency divider circuits131, 132, 136 and 137 included in the jitter removing section 13,respectively. Also in a case where the frequency fclk of the clocksignal Xclk is not lower than 22 MHz, the control section 12 operates inthe same manner as above.

When the frequency fclk of the clock signal Xclk is high (specifically,not lower than 42 MHz), the control section 12 sets the frequencydivision ratio A to a large value (specifically, 200). When thefrequency fclk of the clock signal Xclk is low (specifically, not higherthan 41 MHz), the control section 12 sets the frequency division ratio Ato a small value (specifically, 100). This enables the frequencies ofthe clock signals which the phase comparator 133 receives to fall withinan operation band of the phase comparator 133. The control section 12further sets the frequency division ratios B, C and D so that B=A×D issatisfied. This equalizes the frequency f′clk of the clock signal X′clkoutputted from the jitter removing section 13 to the frequency fclk ofthe clock signal Xclk which the jitter removing section 13 receives.

[Specific Example of Link Command]

As has been described, the control section 12 of the transmissionapparatus 1′ provides the reception apparatus 2′ with band informationindicative of the operation band to which the operation band of thejitter removing section 13 has been changed. In a case where the jittercleaner illustrated in FIG. 10 is used as the jitter removing section13, the control section 12 of the transmission apparatus 1′ provides thereception apparatus 2′ with a link command corresponding to the range ofthe count value outputted from the frequency determining circuit 125.Since the operation band of the jitter removing section 13 (thefrequency division ratios A through D of the respective frequencydivider circuits 131, 132, 136 and 137 included in the jitter removingsection 13) corresponds to the range of the count value outputted fromthe frequency determining circuit 125 (see FIG. 11), the link commandcorresponding to the range of the count value outputted from thefrequency determining circuit 125 is indicative of the operation band ofthe jitter removing section 13.

(a) of FIG. 12 shows a correspondence among (i) the range of thefrequency fclk of the clock signal Xfclk, (ii) the range of the countvalue outputted from the frequency determining circuit 125, and (iii)the link command with which the control section 12 of the transmissionapparatus 1′ provides the reception apparatus 2′.

For example, in a case where the range of the frequency fclk of theclock signal Xclk is not lower than 19 MHz and not higher than 21 MHz,the range of the count value outputted from the frequency determiningcircuit 125 is not less than 435E and not more than 3B91. In this case,the control section 12 of the transmission apparatus 1′ sets thefrequency division ratios A through D of the respective frequencydivider circuits 131, 132, 136 and 137 to 100, 5000, 2 and 50,respectively (see FIG. 11), and provides the reception apparatus 2′ witha link command E0. Also in a case where the frequency fclk of the clocksignal Xclk is not lower than 22 MHz, the control section 12 operates inthe same manner as above.

The control section 22 of the reception apparatus 2′ changes anoperation band of the jitter removing section 23 (frequency divisionratios A through D of respective frequency divider circuits included inthe jitter removing section 23) in accordance with the link commandobtained from the transmission apparatus 1′.

(b) of FIG. 12 shows a correspondence between (i) the link command withwhich the transmission apparatus 1′ provides the control section 22 ofthe reception apparatus 2′ and (ii) the frequency division ratios Athrough D of the respective frequency divider circuits included in thejitter removing section 23.

For example, in a case where the link command with which thetransmission apparatus 1′ provides the control section 22 of thereception apparatus 2′ is E0, the control section 22 of the receptionapparatus 2′ sets, to 100, 5000, 2 and 50, the frequency division ratiosA through D of the respective frequency divider circuits included in thejitter removing section 23, respectively. This equalizes the operationband of the jitter removing section 23 of the reception apparatus 2′(the frequency division ratios A through D of the respective frequencydivider circuits included in the jitter removing section 23) to theoperation band of the jitter removing section 13 of the transmissionapparatus 1′ (the frequency division ratios A through D of therespective frequency divider circuits included in the jitter removingsection 13). Also in a case where the frequency fclk of the clock signalXclk is not lower than 22 MHz, the control section 22 operates in thesame manner as above.

Embodiment 3

The following description will discuss Embodiment 3 of the presentinvention with reference to drawings.

[Configurations of Transmission Apparatus and Reception Apparatus]

Configurations of a transmission apparatus 1″ and a reception apparatus2″ of Embodiment 3 of the present invention will be described withreference to FIG. 13. FIG. 13 is a block diagram illustrating theconfigurations of the transmission apparatus 1″ and the receptionapparatus 2″ of Embodiment 3.

The transmission apparatus 1″ is an apparatus configured to transmit adata signal X to the reception apparatus 2″. The transmission apparatus1″ includes a transmitter 11, a control section 12, and a jitterremoving section 13. The transmitter 11 and the control section 12 whichare included by the transmission apparatus 1″ of Embodiment 3 are blockshaving respective functions identical to those of the transmitter 11 andthe control section 12 which are included by the transmission apparatus1 (particularly, the transmission apparatus 1 illustrated in FIG. 2) ofEmbodiment 1. Therefore, descriptions of the transmitter 11 and thecontrol section 12 which are included by the transmission apparatus 1″of Embodiment 3 are omitted here. The jitter removing section 13included by the transmission apparatus 1″ of Embodiment 3 is a blockhaving a function identical to that of the jitter removing section 13included by the transmission apparatus 1′ of Embodiment 2. Therefore,description of the jitter removing section 13 included by thetransmission apparatus 1″ of Embodiment 3 is omitted here.

Similar to the control section 12 of the transmission apparatus 1′ ofEmbodiment 2, the control section 12 changes an operation band of thejitter removing section 13. That is, the control section 12 changes theoperation band of the jitter removing section 13 to an operation bandcorresponding to a frequency of a clock signal Xclk which frequency hasbeen determined by a frequency determining circuit 125. The controlsection 12 further provides the reception apparatus 2″ with a linkcommand corresponding to the frequency of the clock signal Xclk whichfrequency has been determined by the frequency determining circuit 125.The link command and the operation band of the jitter removing section13 have a correspondence relation via the frequency of the clock signalXclk. Therefore, the link command can be regarded as band informationindicative of the operation band of the jitter removing section 13.

For example, in a case where the jitter cleaner illustrated in FIG. 10is used as the jitter removing section 13, the control section 12changes, to values corresponding to a range of a count value outputtedfrom the frequency determining circuit 125, frequency division ratios Athrough D of respective frequency divider circuits 131, 132, 136 and 137included in the jitter removing section 13. See FIG. 11 as to acorrespondence among (i) a range of a frequency fclk of a clock signalXclk, (ii) the range of the count value outputted from the frequencydetermining circuit 125, and (iii) the frequency division ratios Athrough D of the respective frequency divider circuits 131, 132, 136 and137 included in the jitter removing section 13. What will be laterdescribed with reference to another drawing is a correspondence between(i) the range of the count value outputted from the frequencydetermining circuit 125 and (ii) the link command with which the controlsection 12 of the transmission apparatus 1″provides the receptionapparatus 2″.

The reception apparatus 2″ is an apparatus configured to receive a datasignal X from the transmission apparatus 1″. The reception apparatus 2″includes a receiver 21″ and a control section 22. The receiver21″includes a data signal receiving section 211, a reception processingsection 212, a PLL section 213, a frequency divider circuit 214, and ajitter removing section 215. The data signal receiving section 211 andthe reception processing section 212 which are included by the receiver21″ of Embodiment 3 are blocks having respective functions identical tothose of the data signal receiving section 211 and the receptionprocessing section 212 which are included by the receiver 21 ofEmbodiment 1. Therefore, descriptions of the data signal receivingsection 211 and the reception processing section 212 which are includedby the receiver 21″ of Embodiment 3 are omitted here.

The frequency divider circuit 214 generates, from a clock CLK1reproduced by the data signal receiving section 211, a clock (1/4) CLKwhose frequency is 1/4 as high as that of the clock CLK1, i.e., whosefrequency is 7/8 as high as that of a clock signal Xclk. The jitterremoving section 215 removes jitter included in the clock (1/4) CLK1generated by the frequency divider circuit 214. The PLL section 213restores a clock signal Xclk from the clock (1/4) CLK1′ from which thejitter removing section 215 has removed jitter. Note that the PLLsection 213 may be replaced with a retiming circuit, a frequency dividercircuit or the like whose function is identical to that of a PLLcircuit.

As such, in Embodiment 3, the frequency of the clock (1/4) CLK1 to beprocessed by the jitter removing section 215 is 7/8 as high as that ofthe clock signal Xclk. It is therefore possible to use, as the jitterremoving section 215, a jitter cleaner having a comparatively smalloperation band, e.g., a jitter cleaner having an operation bandapproximately in a range from 19 MHz to 90 MHz. Note that, in a casewhere a jitter cleaner used as the jitter removing section 215 has asufficiently large operation band, the frequency divider circuit 214 canbe omitted.

Similar to the jitter removing section 13 included by the transmissionapparatus 1″, the jitter removing section 215 is configured so that anoperation band is changeable. The control section 22 changes theoperation band of the jitter removing section 215. That is, the controlsection 22 changes the operation band of the jitter removing section 215to an operation band corresponding to the link command obtained from thetransmission apparatus 1″.

For example, in a case where a jitter cleaner whose configuration isidentical to that of the jitter removing section 13 included by thetransmission apparatus 1″ is used as the jitter removing section 215,the control section 22 changes, to values corresponding to the linkcommand obtained from the transmission apparatus 1″, frequency divisionratios A through D of respective frequency divider circuits included inthe jitter removing section 215. What will be described later withreference to another drawing is a correspondence between the linkcommand obtained from the transmission apparatus 1″ and the frequencydivision ratios A through D of the respective frequency divider circuitsincluded in the jitter removing section 215.

As such, a configuration is adopted in which the jitter removing section215 is provided so as to precede the PLL section 213. This makes itpossible to attain a more stable communication performance as comparedwith a configuration where the jitter removing section 215 is providedso as to follow the PLL section 213.

Similar to the transmitter 11 of the transmission apparatus 1 ofEmbodiment 1, the transmitter 11 of the transmission apparatus 1″ ofEmbodiment 3 includes a PLL section 112 (see FIG. 2). Similar to thecontrol section 12 of the transmission apparatus 1 of Embodiment 1, thecontrol section 12 of the transmission apparatus 1″ of Embodiment 3 (i)changes an operation band of the PLL section 112 to an operation bandincluding a frequency of a clock signal Xclk, and (ii) provides thereception apparatus 2″ with band information indicative of the operationband to which the operation band of the PLL section 112 has beenchanged. Similar to the control section 22 of the reception apparatus 2of Embodiment 1, the control section 22 of the reception apparatus 2″ ofEmbodiment 3 obtains the band information from the transmissionapparatus 1″, and changes an operation band of the PLL section 213 tothe operation band indicated by the obtained band information. Thislinks (i) setting of the operation band of the PLL section 112 includedby the transmission apparatus 1″ to (ii) setting of the operation bandof the PLL section 213 included by the reception apparatus 2″.

As such, in Embodiment 3, (i) setting of the operation band of thejitter removing section 13 included by the transmission apparatus 1″ andsetting of the operation band of the jitter removing section 215included by the reception apparatus 2″ are linked to each other, and(ii) the setting of the operation band of the PLL section 112 includedby the transmission apparatus 1″ and the setting of the operation bandof the PLL section 213 included by the reception apparatus 2″ are linkedto each other. Alternatively, it may be such that (i) the setting of theoperation band of the PLL section 112 and the setting of the operationband of the PLL section 213 are not linked to each other, and (ii) onlythe setting of the operation band of the jitter removing section 13 andthe setting of the operation band of the jitter removing section 215 arelinked to each other.

Similar to the transmission apparatus 1 and the reception apparatus 2 ofEmbodiment 1, the transmission apparatus 1″ and the reception apparatus2″ of Embodiment 3 are applicable to a Camera Link system (see FIG. 7).That is, the transmission apparatus 1″ and the reception apparatus 2″ ofEmbodiment 3 are applicable to a camera-side connector and agrabber-side connector of the Camera Link system. In this case, theabove-described link command (the band information indicative of theoperation band of the jitter removing section 13), for example, istransmittable as an internal link signal, together with another controlinformation, from the transmission apparatus 1″ that is the camera-sideconnector to the reception apparatus 2″ that is the grabber-sideconnector.

[Specific Example of Link Command]

(a) of FIG. 14 shows a correspondence among (i) a range of a frequencyfclk of a clock signal Xclk, (ii) a range of a count value outputtedfrom the frequency determining circuit 125, and (iii) a link commandwith which the control section 12 of the transmission apparatus 1″provides the reception apparatus 2″.

For example, in a case where the range of the frequency fclk of theclock signal Xclk is not lower than 19 MHz and not higher than 20 MHz,the range of the count value outputted from the frequency determiningcircuit 125 is not less than 435E and not more than 3E7A. In this case,the control section 12 of the transmission apparatus 1″ provides thereception apparatus 2 with a link command F0. Also in a case where thefrequency fclk of the clock signal Xclk is not lower than 21 MHz, thecontrol section 12 operates in the same manner as above.

(b) of FIG. 14 shows the correspondence between (i) the link commandwhich the control section 22 of the reception apparatus 2″ obtains fromthe transmission apparatus 1″ and (ii) the frequency division ratios Athrough D of the respective frequency divider circuits included in thejitter removing section 215 of the reception apparatus 2″.

For example, in a case where the link command which the control section22 of the reception apparatus 2″obtains from the transmission apparatus1″ is F0, the control section 22 of the reception apparatus 2″ sets, to100, 5600, 2 and 50, the frequency division ratios A through D of therespective frequency divider circuits included in the jitter removingsection 215, respectively. This causes a center frequency of theoperation band of the jitter removing section 215 of the receptionapparatus 2″, the center frequency being determined based on thefrequency division ratios A through D of the respective frequencydivider circuits, to be approximately 7/8 as high as that of theoperation band of the jitter removing section 13 of the transmissionapparatus 1″.

[Modification of Jitter Removing Section]

Modifications of (i) the jitter removing section 13 included by thetransmission apparatus 1″ of Embodiment 3 and (ii) the jitter removingsection 215 included by the reception apparatus 2″ of Embodiment 3 willbe described with reference to FIG. 15. (a) of FIG. 15 is a blockdiagram illustrating the modification of the jitter removing section 13included by the transmission apparatus 1″. (b) of FIG. 15 is a blockdiagram illustrating the modification of the jitter removing section 215included by the reception apparatus 2″.

As illustrated in (a) of FIG. 15, a transmission-side jitter removingsection 13 of this modification includes (i) a first PLL circuit 13 a,(ii) a jitter cleaner 13 b whose operation band is unchangeable (whosefrequency division ratio is unchangeable), and (iii) a second PLLcircuit 13 c.

The first PLL circuit 13 a is a PLL circuit which receives a clocksignal Xclk and outputs an intermediate clock signal whose frequency isN/M as high as that of the clock signal Xclk. The numbers “N” and “M” ofthe first PLL circuit 13 a are set by the control section 22. Theintermediate clock signal outputted by the first PLL section 13 a issupplied to the jitter cleaner 13 b.

The jitter cleaner 13 b removes jitter included in the intermediateclock signal outputted by the first PLL circuit 13 a. The second PLLcircuit 13 c is a PLL circuit which (i) receives an intermediate clocksignal supplied from the jitter cleaner 13 b and (ii) outputs a clocksignal whose frequency is M/N as high as that of the receivedintermediate clock signal. The numbers “N” and “M” of the second PLLcircuit 13 c are set by the control section 22.

As illustrated in (b) of FIG. 15, a reception-side jitter removingsection 215 of this modification includes (i) a first PLL circuit 215 a,(ii) a jitter cleaner 215 b whose operation band is unchangeable (whosefrequency division ratio is unchangeable), and (iii) a second PLLcircuit 215 c.

The first PLL circuit 215 a is a PLL circuit which receives a clock(1/4) CLK and outputs an intermediate clock whose frequency is N/M ashigh as that of the clock (1/4) CLK1. The numbers “N” and “M” of thefirst PLL circuit 215 a are set by the control section 22. Theintermediate clock outputted by the first PLL section 215 a is suppliedto the jitter cleaner 215 b.

The jitter cleaner 215 b removes jitter included in the intermediateclock signal outputted by the first PLL circuit 215 a. The second PLLcircuit 215 c is a PLL circuit which (i) receives an intermediate clocksupplied from the jitter cleaner 215 b and (ii) outputs a clock whosefrequency is M/N as high as that of the received intermediate clock. Thenumbers “N” and “M” of the second PLL circuit 215 c are set by thecontrol section 22.

An operation band of the transmission-side jitter removing section 13 ofthis modification is changed by changing the numbers “N” and “M” of thePLL circuits 13 a and 13 c included in the jitter removing section 13.Since the operation band of the jitter cleaner 13 b is unchangeable, atoo high or low frequency of the clock signal Xclk will cause a casewhere a frequency of a clock signal to be supplied to the jitter cleaner13 b exceeds an upper limit of the operation band of the jitter cleaner13 b or is lower than a lower limit of the operation band of the jittercleaner 13 b. However, it is possible to prevent such a case fromoccurring by changing the operation band of the jitter removing section13 to an operation band corresponding to the frequency of the clocksignal Xclk, that is, by setting the numbers “N” and “M” to valuescorresponding to the frequency of the clock signal Xclk. The sameapplies to changing an operation band of the reception-side jitterremoving section 215 of this modification.

The control section 12 of the transmission apparatus 1″ including thejitter removing section 13 of this modification (i) sets the numbers “M”and “N” of the PLL circuits 13 a and 13 c to values corresponding to afrequency of a clock signal Xclk which frequency has been determined bythe frequency determining circuit 125, and (ii) provides the receptionapparatus 2″ with a link command corresponding to the frequency of theclock signal Xclk which frequency has been determined by the frequencydetermining circuit 125.

FIG. 16 shows an example correspondence among (i) a range of a frequencyfclk of a clock signal Xclk, (ii) a range of a count value outputtedfrom the frequency determining circuit 125, and (iii) the number “N” and“M” of the PLL circuits 13 a and 13 c included in the jitter removingsection 13. (a) of FIG. 17 shows an example correspondence among (i) arange of a frequency fclk of a clock signal Xclk, (ii) a range of acount value outputted from the frequency determining circuit 125, and(iii) a link command with which the control section 12 of thetransmission apparatus 1″ provides the reception apparatus 2″.

The control section 22 of the reception apparatus 2″ including thejitter removing section 215 of this modification sets the numbers “M”and “N” of the PLL circuits 215 a and 215 c to values corresponding tothe link command obtained from the transmission apparatus 1″.

(b) of FIG. 17 shows a correspondence between (i) the link command whichthe control section 22 of the reception apparatus 2″ obtains from thetransmission apparatus 1″ and (ii) the numbers “M” and “N” of the PLLcircuits 215 a and 215 c included in the jitter removing section 215.

For example, in a case where the frequency fclk of the clock signal Xclkis 25.0 MHz, the range of the count value outputted from the frequencydetermining circuit 125 is 363D to (3298) in the table illustrated inFIG. 16. In this case, the control section 12 of the transmissionapparatus 1″ sets, to 210 and 512, the numbers “N” and “M” of the PLLcircuits 13 a and 13 c included in the jitter removing section 13,respectively. In addition, in the case where the frequency fclk of theclock signal Xclk is 25.0 MHz, the range of the count value outputtedfrom the frequency determining circuit 125 is 363D to (3200) in thetable illustrated in (a) of FIG. 17. In this case, the control section12 of the transmission apparatus 1″ provides the reception apparatus 2″with a link command “32”. Upon reception of the link command “32”, thecontrol section 22 of the reception apparatus 2′ sets, to 244 and 512,the numbers “N” and “M” of the PLL circuits 215 a and 215 c included inthe jitter removing section 215, respectively, according to the tableillustrated in (b) of FIG. 17. Note that the reason why the number “N”of the PLL circuits 215 a and 215 c included in the reception-sidejitter removing section 215 is 244/210 (approximately 8/7) as large asthat of the PLL circuits 13 a and 13 c included in the transmission-sidejitter removing section 13 is that a frequency of a clock (1/4) CLK1 tobe processed in the reception-side jitter removing section 215 is 7/8 ashigh as that of a clock Xclk to be processed in the transmission-sidejitter removing section 13.

This modification has described a case where the number “M” is constant(512) whereas the number “N” changes depending on the range of the countvalue outputted from the frequency determining section 125. However, thepresent invention is not limited to the case. For example, a case may beemployed in which the number “N” is constant whereas the number “M”changes depending on the range of the count value outputted from thefrequency determining section 125. Alternatively, a case may be employedin which both the numbers “N” and “M” change depending on the countvalue outputted from the frequency determining section 125.

Note that the jitter removing section 13 illustrated in (a) of FIG. 15,and the jitter removing section 215 illustrated in (b) of FIG. 15 can beused as the jitter removing section 13 included by the transmissionapparatus 1′ of Embodiment 2, and the jitter removing section 23included by the reception apparatus 2′ of Embodiment 2, respectively.

<<Summary>>

As has been described, a transmission apparatus of an embodiment isconfigured to include: a PLL (Phase Looked Loop) section which generatesa first clock on the basis of a clock signal given to the PLL section; adata signal transmitting section which transmits, with use of the firstclock generated by the PLL section, a data signal given to the datasignal transmitting section together with the clock signal being givento the PLL section; and a control section which measures a frequency ofthe clock signal with use of a second clock independent of the firstclock, the control section (i) changing setting of the transmissionapparatus to setting corresponding to a measured frequency and (ii)providing, with setting information indicative of the setting to whichthe setting of the transmission apparatus has been changed, a receptionapparatus to which the data signal is to be transmitted.

A reception apparatus of an embodiment is configured to include: a datasignal receiving section which (i) reproduces a clock synchronizing witha first clock with use of which a transmission apparatus transmits adata signal, the data signal receiving section reproducing the clockfrom the data signal which the transmission apparatus has transmittedand (ii) receives, with use of the clock synchronizing with the firstclock, the data signal which the transmission apparatus has transmitted;a clock signal restoring section which restores, on the basis of theclock synchronizing with the first clock, a clock signal with referenceto which the transmission apparatus generates the first clock; and acontrol section which (i) obtains, from the transmission apparatus,setting information indicative of setting of the transmission apparatusand (ii) changes setting of the reception apparatus to the settingindicated by the setting information.

A transmission method of an embodiment is configured to include thesteps of: (a) generating a first clock on the basis of a clock signalgiven; (b) transmitting, with use of the first clock generated in thestep (a), a data signal given together with the clock signal beinggiven; (c) measuring a frequency of the clock signal with use of asecond clock independent of the first clock; (d) changing setting of atransmission apparatus to setting corresponding to a measured frequency;and (e) providing, with setting information indicative of the setting towhich the setting of the transmission apparatus has been changed, areception apparatus to which the data signal is to be transmitted.

A reception method of an embodiment is configured to include the stepsof: reproducing a clock synchronizing with a first clock with use ofwhich a transmission apparatus transmits a data signal, the clock beingreproduced from the data signal which the transmission apparatus hastransmitted; receiving, with use of the clock synchronizing with thefirst clock, the data signal which the transmission apparatus hastransmitted; restoring, on the basis of the clock synchronizing with thefirst clock, a clock signal with reference to which the transmissionapparatus generates the first clock; obtaining, from the transmissionapparatus, setting information indicative of setting of the transmissionapparatus; and changing setting of a reception apparatus to the settingindicated by the setting information.

According to the configuration, the transmission apparatus measures thefrequency of the clock signal with use of the second clock independentof the first clock. This enables the transmission apparatus to graspfluctuation in the frequency of the clock signal (in a case where thetransmission apparatus measures the frequency of the clock signal withuse of the first clock, the transmission apparatus cannot grasp thefluctuation in the frequency of the clock signal). According to theconfiguration, the transmission apparatus further (i) changes thesetting of the transmission apparatus to the setting corresponding tothe measured frequency of the clock signal and (ii) notifies thereception apparatus of the setting to which the setting of thetransmission apparatus has been changed. This makes it possible toconform the setting of the transmission apparatus to setting of thereception apparatus.

Therefore, according to the configuration, it is possible to improvestability of communication during transmission and reception of databetween the transmission apparatus and the reception apparatus.

It is preferable to configure the transmission apparatus of theembodiment such that the PLL section is configured so that an operationband is changeable, and the control section changes the operation bandof the PLL section to an operation band including the measuredfrequency, and provides the reception apparatus, as the settinginformation, with band information indicative of the operation band towhich the operation band of the PLL section has been changed.

According to the configuration, it is possible to equalize the operationband of the PLL section of the transmission apparatus to an operationband of a PLL section of the reception apparatus.

It is preferable to configure the transmission apparatus of theembodiment to further include a frequency converting section whichconverts the clock signal to an intermediate clock signal whosefrequency is not more than 1/2 as high as that of the second clock, andthe control section measuring the frequency of the clock signal withreference to the intermediate clock signal.

In a case where the frequency of the clock signal is more than 1/2 ashigh as that of the second clock, it is not possible to correctlymeasure the frequency of the clock signal with use of the second clock(sampling theorem). On the other hand, according to the configuration,even in the case where the frequency of the clock signal is more than1/2 as high as that of the second clock, it is possible to correctlymeasure the frequency of the clock signal with use of the second clock.

It is preferable to configure the transmission apparatus of theembodiment so that the PLL section includes (i) a first PLL circuitgenerating a first original clock and having a first operation band,(ii) a second PLL circuit generating a second original clock whosefrequency is different from that of the first original clock and havinga second operation band which partially overlaps with the firstoperation band, (iii) a switch which switches between connecting thefirst PLL circuit to the data signal transmitting section and connectingthe second PLL circuit to the data signal transmitting section, and (iv)a frequency converting circuit being provided at least one of (a)between the first PLL circuit and the switch and (b) between the secondPLL circuit and the switch, and the frequency converting circuitequalizing (i) the frequency of the first original clock to be suppliedto the switch and (ii) the frequency of the second original clock to besupplied to the switch to each other.

According to the configuration, the PLL section includes (i) the firstand second PLL circuits whose operation bands partially overlap witheach other and (ii) the switch which switches between connecting thefirst PLL circuit and connecting the second PLL circuit. Therefore, itis possible to change the operation band of the PLL section by causingthe switch to switch in accordance with the frequency of the clocksignal which frequency has been measured by the transmission apparatus.Particularly, according to the configuration, the first PLL circuit isdifferent in multiplication constant from the second PLL circuit. On theother hand, the PLL section includes the frequency converting circuit.Therefore, even in a case where an operation band is changed, it ispossible to set, to be constant, a multiplication constant of afrequency of the first clock generated by the PLL section.

Therefore, according to the configuration, it is possible to moresuitably change the operation band of the PLL section.

It is preferable to configure the transmission apparatus of theembodiment to further include a jitter removing section (i) whichremoves jitter included in the clock signal which the PLL sectionreceives and (ii) whose operation band is changeable, the controlsection (i) changing the operation band of the jitter removing sectionto an(the) operation band including the measured frequency and (ii)providing the reception apparatus, as the setting information, bandinformation indicative of the operation band to which the operation bandof the jitter removing section has been changed.

According to the configuration, it is possible to equalize the operationband of the jitter removing section of the transmission apparatus to anoperation band of a jitter removing section of the reception apparatus.

It is preferable to configure the reception apparatus of the embodimentsuch that the PLL section is configured so that an operation band ischangeable, and the control section (i) obtains, as the settinginformation, from the transmission apparatus, band informationindicative of the operation band of the PLL section included by thetransmission apparatus and (ii) changes, to the operation band indicatedby the band information, the operation band of the PLL section includedby the reception apparatus.

According to the configuration, it is possible to equalize the operationband of the PLL section of the reception apparatus to the operation bandof the PLL section of the transmission apparatus.

It is preferable to configure the reception apparatus of the embodimentto further include a jitter removing section (i) which removes jitterincluded in the clock signal to be supplied from the clock signalrestoring section and (ii) whose operation band is changeable, and thecontrol section (i) obtaining, as the setting information, from thetransmission apparatus, band information indicative of an operation bandof a jitter removing section included by the transmission apparatus and(ii) changing, to the operation band indicated by the band information,the operation band of the jitter removing section included by thereception apparatus.

According to the configuration, it is possible to equalize the operationband of the jitter removing section of the reception apparatus to theoperation band of the jitter removing section of the transmissionapparatus.

It is preferable to configure the reception apparatus of the embodimentto further include a jitter removing section (i) which removes jitterincluded in the clock signal which the clock signal restoring sectionreceives and (ii) whose operation band is changeable, and the controlsection (i) obtaining, as the setting information, from the transmissionapparatus, band information indicative of an operation band of a jitterremoving section included by the transmission apparatus and (ii)changing, to the operation band indicated by the band information, theoperation band of the jitter removing section included by the receptionapparatus.

According to the configuration, it is possible to set the operation bandof the jitter removing section of the reception apparatus so as tocorrespond to the operation band of the jitter removing section of thetransmission apparatus. Furthermore, since the jitter removing sectionis provided so as to precede the PLL section, it is possible to attain amore stable communication performance as compared with a case where thejitter removing section is provided so as to follow the PLL section.

It is preferable to configure the reception apparatus of the embodimentso that a frequency divider circuit which decreases a frequency of theclock is provided so as to precede the jitter removing section.

According to the configuration, it is possible to use, as the jitterremoving section, a jitter cleaner having a smaller operation band.

It is preferable to configure the reception apparatus of the embodimentso that the jitter removing section includes (i) a first frequencydivider circuit which generates an intermediate clock whose frequency isN/M as high as that of an input clock, (ii) a jitter cleaner whichremoves jitter included in the intermediate clock, and (iii) a secondfrequency divider circuit which generates an output clock whosefrequency is M/N as high as that of the intermediate clock from whichthe jitter cleaner has removed the jitter.

According to the configuration, it is possible to configure the jitterremoving section with a jitter cleaner whose operation band isunchangeable.

Note that the present invention encompasses a transmission and receptionsystem including the transmission apparatus and the reception apparatus.In the transmission and reception system, for example, the transmissionapparatus and the reception apparatus are connected to each other via asignal line via which the transmission apparatus and the receptionapparatus transmit and receive internal control information, and thesetting information is transmitted and received via the signal line.

According to the configuration, the setting information is transmittedand received via the signal line via which the internal controlinformation is transmitted and received. Therefore, the transmission andreception system (e.g., a Camera Link system) including the signal linevia which the internal control information is transmitted and receivedcan transmit and receive setting information without including anyadditional signal line.

The present invention also encompasses a transmission and receptionsystem including: a first transmission path including (i) a firsttransmission apparatus that is the transmission apparatus of theembodiment and (ii) a first reception apparatus that is the receptionapparatus of the embodiment; and a second transmission path including(i) a second transmission apparatus that is the transmission apparatusof the embodiment and (ii) a second reception apparatus that is thereception apparatus of the embodiment, the first reception apparatusincluded by the first transmission path and the second receptionapparatus included by the second transmission path sharing the settinginformation with each other.

According to the configuration, it is possible to share settinginformation between transmission and reception systems different fromeach other. This allows a more stable communication.

<<Additional Description>>

The present invention is not limited to the embodiments, but can bealtered by a skilled person in the art within the scope of the claims.An embodiment derived from a proper combination of technical means eachdisclosed in a different embodiment is also encompassed in the technicalscope of the present invention.

For example, Embodiment 1 has described a case where setting of the PLLsection of the transmission apparatus is uniformalized to setting of thePLL section of the reception apparatus, and Embodiment 2 has described acase where setting of the jitter removing section of the transmissionapparatus is uniformalized to setting of the jitter removing section ofthe reception apparatus. However, the present invention is not limitedto the cases. For example, setting (Reconfiguration) of FPGA, setting offilter constant, setting of various indicators may be uniformalizedbetween a transmission apparatus and a reception apparatus. Moreover, anexample application can be employed in which, for example, a receptionapparatus is notified of whether or not a clock determined in atransmission apparatus exists (whether or not a camera is beingconnected), and when the reception apparatus is notified that no clockexists, the reception apparatus stops supply of electric power.Alternatively, an example application to setting and control of anexternal apparatus may be employed in which example application acontrol section which controls front wheels of an automobile (i) isnotified of the number of revolutions of rear wheels of the automobile,and (ii) optimizes the number of revolutions of the front wheels.

INDUSTRIAL APPLICABILITY

The present invention is generally and widely applicable to atransmission system which transmits a data signal accompanied by a clocksignal. The present invention is applicable to, for example, CameraLink.

REFERENCE SIGNS LIST

-   1, 1′, and 1″: Transmission apparatus-   11: Transmitter-   111: Data signal transmitting section-   112: PLL section-   112 a: PLL circuit (first PLL circuit)-   112 b: Frequency converting circuit-   112 c: PLL circuit (second PLL circuit)-   112 d: Switch-   112 e: Frequency converting circuit-   113: Frequency converting section-   113 a: 2¹⁶ frequency divider circuit-   12: Control section-   13: Jitter removing section-   2, 2′, and 2″: Reception apparatus-   21: Receiver-   211: Data signal receiving section-   212: Reception processing section-   213: PLL section (clock signal restoring section)-   214: Frequency divider circuit-   215: Jitter removing section-   22: Control section-   23: Jitter removing section-   3: Cable-   4: Transmission apparatus-   42: Control section-   5: Reception apparatus-   52: Control section-   6: Cable

1. A transmission apparatus, comprising: a PLL (Phase Looked Loop)section which generates a first clock on the basis of a clock signalgiven to the PLL section; a data signal transmitting section whichtransmits, with use of the first clock generated by the PLL section, adata signal given to the data signal transmitting section together withthe clock signal being given to the PLL section; and a control sectionwhich measures a frequency of the clock signal with use of a secondclock independent of the first clock, the control section (i) changingsetting of the transmission apparatus to setting corresponding to ameasured frequency and (ii) providing, with setting informationindicative of the setting to which the setting of the transmissionapparatus has been changed, a reception apparatus to which the datasignal is to be transmitted.
 2. The transmission apparatus as set forthin claim 1, wherein the PLL section is configured so that an operationband is changeable, and the control section changes the operation bandof the PLL section to an operation band including the measuredfrequency, and provides the reception apparatus, as the settinginformation, with band information indicative of the operation band towhich the operation band of the PLL section has been changed.
 3. Thetransmission apparatus as set forth in claim 2, further comprising afrequency converting section which converts the clock signal to anintermediate clock signal whose frequency is not more than 1/2 as highas that of the second clock, and the control section measuring thefrequency of the clock signal with reference to the intermediate clocksignal.
 4. The transmission apparatus as set forth in claim 2, whereinthe PLL section includes (i) a first PLL circuit generating a firstoriginal clock and having a first operation band, (ii) a second PLLcircuit generating a second original clock whose frequency is differentfrom that of the first original clock and having a second operation bandwhich partially overlaps with the first operation band, (iii) a switchwhich switches between connecting the first PLL circuit to the datasignal transmitting section and connecting the second PLL circuit to thedata signal transmitting section, and (iv) a frequency convertingcircuit being provided at least one of (a) between the first PLL circuitand the switch and (b) between the second PLL circuit and the switch,and the frequency converting circuit equalizing (i) the frequency of thefirst original clock to be supplied to the switch and (ii) the frequencyof the second original clock to be supplied to the switch to each other.5. The transmission apparatus as set forth in claim 1, furthercomprising a jitter removing section (i) which removes jitter includedin the clock signal which the PLL section receives and (ii) whoseoperation band is changeable, the control section (i) changing theoperation band of the jitter removing section to an(the) operation bandincluding the measured frequency and (ii) providing the receptionapparatus, as the setting information, band information indicative ofthe operation band to which the operation band of the jitter removingsection has been changed.
 6. A reception apparatus, comprising: a datasignal receiving section which (i) reproduces a clock synchronizing witha first clock with use of which a transmission apparatus transmits adata signal, the data signal receiving section reproducing the clockfrom the data signal which the transmission apparatus has transmittedand (ii) receives, with use of the clock synchronizing with the firstclock, the data signal which the transmission apparatus has transmitted;a clock signal restoring section which restores, on the basis of theclock synchronizing with the first clock, a clock signal with referenceto which the transmission apparatus generates the first clock; and acontrol section which (i) obtains, from the transmission apparatus,setting information indicative of setting of the transmission apparatusand (ii) changes setting of the reception apparatus to the settingindicated by the setting information.
 7. The reception apparatus as setforth in claim 6, wherein the clock signal restoring section is a PLL(Phase Looked Loop) section whose operation band is changeable, and thecontrol section (i) obtains, as the setting information, from thetransmission apparatus, band information indicative of an operation bandof a PLL section included by the transmission apparatus and (ii)changes, to the operation band indicated by the band information, theoperation band of the PLL section included by the reception apparatus.8. The reception apparatus as set forth in claim 6, further comprising ajitter removing section (i) which removes jitter included in the clocksignal to be supplied from the clock signal restoring section and (ii)whose operation band is changeable, and the control section (i)obtaining, as the setting information, from the transmission apparatus,band information indicative of an operation band of a jitter removingsection included by the transmission apparatus and (ii) changing, to theoperation band indicated by the band information, the operation band ofthe jitter removing section included by the reception apparatus.
 9. Thereception apparatus as set forth in claim 6, further comprising a jitterremoving section (i) which removes jitter included in the clock signalwhich the clock signal restoring section receives and (ii) whoseoperation band is changeable, and the control section (i) obtaining, asthe setting information, from the transmission apparatus, bandinformation indicative of an operation band of a jitter removing sectionincluded by the transmission apparatus and (ii) changing, to theoperation band indicated by the band information, the operation band ofthe jitter removing section included by the reception apparatus.
 10. Thereception apparatus as set forth in claim 9, wherein a frequency dividercircuit which decreases a frequency of the clock is provided so as toprecede the jitter removing section.
 11. The reception apparatus as setforth in claim 8, wherein the jitter removing section includes (i) afirst frequency divider circuit which generates an intermediate clockwhose frequency is N/M as high as that of an input clock, (ii) a jittercleaner which removes jitter included in the intermediate clock, and(iii) a second frequency divider circuit which generates an output clockwhose frequency is M/N as high as that of the intermediate clock fromwhich the jitter cleaner has removed the jitter.
 12. A transmission andreception system, comprising: a transmission apparatus; and a receptionapparatus, the transmission apparatus comprising: a PLL (Phase LookedLoop) section which generates a first clock on the basis of a clocksignal given to the PLL section; a data signal transmitting sectionwhich transmits, with use of the first clock generated by the PLLsection, a data signal given to the data signal transmitting sectiontogether with the clock signal being given to the PLL section; and acontrol section which measures a frequency of the clock signal with useof a second clock independent of the first clock, the control section(i) changing setting of the transmission apparatus to settingcorresponding to a measured frequency and (ii) providing, with settinginformation indicative of the setting to which the setting of thetransmission apparatus has been changed, the reception apparatus towhich the data signal is to be transmitted, the reception apparatuscomprising: a data signal receiving section which (i) reproduces a clocksynchronizing with a first clock with use of which the transmissionapparatus transmits a data signal, the data signal receiving sectionreproducing the clock from the data signal which the transmissionapparatus has transmitted and (ii) receives, with use of the clocksynchronizing with the first clock, the data signal which thetransmission apparatus has transmitted; a clock signal restoring sectionwhich restores, on the basis of the clock synchronizing with the firstclock, a clock signal with reference to which the transmission apparatusgenerates the first clock; and a control section which (i) obtains, fromthe transmission apparatus, the setting information which is provided bythe transmission apparatus and (ii) changes setting of the receptionapparatus to the setting indicated by the setting information.
 13. Thetransmission and reception system as set forth in claim 12, wherein thetransmission apparatus and the reception apparatus are connected to eachother via a signal line via which the transmission apparatus and thereception apparatus transmit and receive internal control information,and the setting information is transmitted and received via the signalline.